My boat currently has four 6volt (T105) house batteries that I am replacing. This may be a stupid question but 2 of the four are in good condition. Can I keep 2, properly connecting them, to have a house bank of 6? Charging unit is 50amp. Thoughts please. Thx

Conventional wisdom sez batteries are like draft horses -- the team works only as hard as the weakest (or laziest) horse. So CW sez never mix new batteries with old, because the old ones will drag the whole bank down. New batts will tire themselves trying to bring old ones up to snuff.

OTOH, IF you are sure those old batts really are good, and the new ones are same size and type, then more battery capacity is always better than less. Equalize as often as possible, especially if you have 3 or more parallel strings. Once a week is not too often. Luck!

If all your batteries are the same AGE...my guess is that the 2 OK ones are on their last legs and it is not a good idea to mix quite old batteries with new ones. Your charger is big enough for dockside use on a 6 battery bank...but would be undersized in cruising mode where you would want something about double that size.

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